The Simaroubaceae or Quassia family of flowering plants is a small family with less than 20 genera. Plants are mostly tropical and subtropical.

In North America than are approximately 11 genera with 15 accepted taxa overall. Arizona has two species; Ailanthus altissima, tree of heaven and Castela emoryi, Crucifixion Thorn. The Plant List describes 19 plant genera and 121 accepted species names.

The family is known for medicinal plants and species used for furniture and flooring. The popular Tree-of-Heaven, Ailanthus altissima and Amargo, Quassia amara from South America are also well known. Amargo or Bitter-ash, Quassia amara, has properties for uses as an insecticide and food additive as well.

Tree-of-Heaven, Ailanthus altissima is an invasive tree in Arizona and in the southwestern United States. This plant is listed in New Mexico as a "noxious weed".